This invention relates to novel liquid agricultural solution concentrates which, because of solution synergism, have improved properties, e.g., lower crystallization temperatures. These concentrates are useful as herbicides. The active component in the concentrates is a mixture of 1-(3,4-dichlorophenyl)-3-methoxy-3-methylurea, hereinafter called linuron, and 2-chloro-N-isopropylacetanilide, hereinafter called propachlor, or 2-chloro-2',6'-diethyl-N-(methoxymethyl)-acetanilide, hereinafter called alachlor.
The invention further relates to the method of preparing solution concentrates of linuron by combining linuron with a chloroacetanilide selected from the group consisting of propachlor and alachlor in a suitable organic solvent.
Linuron, propachlor and alachlor are herbicides that have been found wide application in weed control programs. It is also known that combinations of linuron and propachlor, as well as linuron and alachlor, exhibit outstanding weed control in corn, sorghum and soybeans both in pre-emergence and post-emergence applications.
Linuron and propachlor have been prepared for use either as granules or as wettable powders. Because of the irritating and toxic nature of propachlor, the dustiness of dry formulations such as wettable powders represents not only an irritation, but also an actual hazard to persons carelessly handling these formulations. This hazard is of particular importance in the manufacture of wettable powders in which the requirement of dust-tight equipment increases the cost and difficulty of producing the formulation. The properties of linuron are such that a solution concentrate is difficult to produce.
Agricultural weed killers, like many other formulated products, must meet a variety of exacting requirements before they are commercially useful. In the case of liquid formulations, they must be stable in storage both at high and low temperatures. Concentrates for application in water must emulsify well when diluted at many different concentrations with water of different types and hardness.
It is known that solution concentrates of linuron, at economically practical concentrations, are not stable when in cold temperature storage. Linuron crystals will form in the concentrates upon storage at moderately low or even room temperatures. When crystallization occurs in large containers as, for example, in a 30-gallon drum in a warehouse, such crystals form dense, thick layers at the bottom of the drum. It is usually impractical or at least very difficult to re-establish a homogeneous solution even when the contents of the drum are warmed. It was, therefore, believed that dry formulations such as wettable powders and granules, were the most acceptable type for formulations containing linuron as an active ingredient.